The invention relates to a device for fitting a sleeve on a container such as a bottle or a similar object, said device comprising a double-walled bush with its inner wall perforated and the interior annular space of the bush being connectable to a vacuum line for generating underpressure within the interior space and sucking a sleeve inserted in said bush against the inner wall so that a container can be brought into the sleeve whereupon the connection with the vacuum line is disconnected.
Devices of this kind are disclosed in U.S. Pat. Nos. 3,841,940, 5,715,651, French Pat. No. 2,669,908, and European Pat. No. 0,109,105.
In the device of the U.S. Pat. No. 3,841,940 the axis of the bush extends almost horizontally and the upper part of the inner wall can be moved vertically in relation to the lower part. By this it should be guaranteed that the sleeve, being brought into the bush in a more or less folded position, will properly engage the inner wall. Due to the fact that the upper part of the inner wall is movable, leakage of air along the end edges may occur. Therefore, there is no guarantee that the sleeve will properly contact the inner wall. When sealings are applied between the parts, these will cause friction, causing the movement of the upper part of the inner wall to be counteracted.
Further, it is difficult to put a sleeve into the bush time after time, this being particularly laborious. This will cause the production rate of the device to be low.
In case of U.S. Pat. No. 5,715,651 a separated sleeve is brought on a device being formed by a fixed suction surface in the form of a comb conprising spaced teeth. Subsequently, the sleeve is taken up by stretchers. The stretchers are moved apart so that the sleeve can be fitted on a container. Thus, the sleeve must be able to withstand a considerable stretch and withdrawing the stretchers out of the sleeve and along the wall of the container may cause difficulties. This does not guarantee appropriate functioning of the device.
French Pat. No. 2,669,908 describes a device in which two resilient plates, being flat in their starting positions, with a sleeve between them, are received between two pairs of clamping jaws. The sleeve is drawn against the plates in that the plates are provided with a number of openings to which pipes connected to a vacuum source are connected. The clamping jaws are pushed towards each other to bring the plates in a bent shape so that together they bring the sleeve in a somewhat circular shape.
This involves a complicated structure and operation. Further, there is a risk that the sleeve will not take up the appropriate form or will be damaged on pushing the resilient plates towards each other.
European Pat. No. 0,109,105 shows a device for cutting a part, in the shape of a sleeve, from a flattened plastic tube drawn from a supply roller. Said sleeve being directly brought upon a container. This, however, is not always possible e.g. when the surface of the container is somewhat wet.
It is an object of this invention to provide a device by which the sleeves will be fitted on the containers in the right way, said device having a high capacity. To that end it is provided for, that the device comprises a number of bushes the inner and outer walls of which are fixedly connected to each other, the axes of said bushes being directed vertically, positioning means for the bushes being present so that a sleeve, obtained by cutting-off a part of a flattened plastic tube drawn from a supply roller, can be slid into a bush in vertical direction and can be sucked against the inner wall of it, whereupon the positioning means can slide the bush and the sleeve across a container and the connection with the vacuum line can be disconnected. So the double-walled bush need only be moved up and down, in such a way that it is situated above a container and can take up a sleeve, while subsequently being moved downwards so that it is positioned around the container. Then, the underpressure is released and the bush is returned to its initial position.
To prevent the sleeve from moving up again with the bush, means for blowing hot air onto the lower edge of the sleeve when the bush is in its lowermost position on the container can be provided for.
To that end the outer wall of the bush can be provided with a downwards extending portion such that a chamber is obtained to which a line for hot air can be connected. Now during upward movement of the bush, the sleeve is shrunk simultaneously, no separate shrinking process being necessary.
It has turned out that it is not absolutely necessary to bring the sleeve in the spread state before it is inserted into the bush. It is desirable, that the sleeve will engage a given portion of the inner circumference of the inner wall of the bush. When this would not be the case, the suction force acting on the sleeve might be insufficient to bring the sleeve in the appropriate shape before it is slid onto a container.
It should be taken into consideration, however, that a certain positive tolerance might exist in the circumferential length of the sleeve. In order to accommodate this the inner wall of the bush will be provided with at least one outwardly directed slot. In order to facilitate accommodation of the overmeasure of material said inner wall of the bush might be provided with more slots.
In particular, a stationary stop member for the sleeve will be present underneath the bush, at the position where a sleeve is inserted into it.
Owing to this, the sleeve can be brought on the appropriate position within the bush before a vacuum is generated in the internal space of the bush.
Such a stop member can be in the shape of a substantially horizontally extending rod being situated at some distance below the bush at the position where the sleeve is inserted into said bush, and which, on moving the bush or the rod substantially in horizontal direction, will closely engage the bottom side of the bush.
This gives the advantage that the sleeve, after first having been slid into the bush till beyond its bottom plane, is brought to the correct position in the bush by the stop member. When the stop member is situated directly below the bush, at the position where the sleeve is inserted into it, a bouncing movement of the sleeve may occur. This would not guarantee that the sleeve is at the appropriate location in the bush when the bush is connected to the vacuum line.
In the known way, the device will comprise a turret in which containers are brought onto a rotating disc from which disc they will be removed after a certain rotation of said disc, the number of bushes being at least equal to the number of containers which can be present on said disc and the guiding member of each bush being slidable along a substantially vertically extending guide connected to the disc.
In the device according to the invention, the bushes are moved in vertical direction, to which end a curve track fixedly mounted in the device is used, against which the guide member of the bush is drawn downwards by means of a spring, in which the sleeve is inserted into the bush at almost the highest point of the track.
This gives the advantage, that when the downward movement of the bush is prevented for some reason, the bush can be kept at a higher position against the action of said spring. This prevents blocking of the device with possible harmful consequences.
Since the vacuum line extending to a bush should rotate along with the disc of the turret, it can be provided for, that the vacuum lines of the bushes situated on the turret are connected to an annular vacuum switching plate extending around the rotary shaft of the disc of the turret and moving along with it, or being part of it, an opening in the vacuum switching plate during part of its rotation communicating with a stationary arranged vacuum chamber situated underneath the switching plate.
In order to provide for, that the bush provided with a sleeve slides down across a container in the appropriate way, means for holding a container positioned on the disc of a turret will be provided for.
During rotation of the disc, a centrifugal force will be exerted on the container, as a result of which the container might be able to move in relation to the disc.
The means for keeping a container in its place on the disc of the turret can be in the form of openings in the disc which can be connected to at least one vacuum chamber situated below the disc. Often it might be sufficient to hold the containers only when bringing them onto the disc and removing them from it.
In certain cases, it is desirable, that the sleeve extends across a part of the bottom of a container. In that case it is provided for, that each container is positioned on a platform being supported movably in vertical direction in the disc of the turret and being provided with a connection for a vacuum line, said platform supporting only the central part of the bottom of a container.
When the bottom of a container does not engage the disc in the appropriate way, generating underpressure below the container will be useless. In that case, it can be provided for, that the disc has a number of openings for each container, to wit at least three, through which pins can be slid from below till beyond the surface of the disc, which will be situated around the container, with the pins being mounted on a support member being movable in vertical direction by operating means.
The operating means for moving the pin-bearing support member up and down can be in the form of a curve track fixedly mounted below the disc of the turret.
It will be obvious, that the means for holding the container on the disc must be activated immediately after the container has been placed on the disc. After that, the means might be switched-off depending on the design of the turret.
The inner wall of the bush need not necessarily have a cylindrical shape. It can also have a more rectangular or oval shape and thus be suitable for fitting a sleeve onto a container having a corresponding cross-sectional shape. Generally, then it will be necessary that a sleeve is inserted into the bush in a certain way. Namely, a print present on the sleeve then will have to be visible on the container in the desired way. Thus, the sleeve should be guided more carefully on insertion into the bush.
The device described above has proven to function very reliably already at a relatively small underpressure in the double-walled bush. When applying a relatively high underpressure, it is possible to process so-called xe2x80x9cstretch sleevesxe2x80x9d.
The invention also comprises a method of using the device described above, said method being characterized in that a sleeve is cut-off from a flattened plastic tube drawn from a supply roller, said sleeve being slid vertically into a double-walled bush having its inner wall perforated, air being drawn from the space around the inner wall so that the sleeve is pressed against the inner wall, the bush being slid across a container, the underpressure in the space being removed, a stream of hot air being directed at the lower edge of the sleeve and the bush being returned to its initial position.
The nature, utility, and further features of this invention will be more clearly apparent from the following description of a preferred embodiment of the invention when read in conjunction with the accompanying drawings.